Various technologies for assisting drivers of vehicles are developed, and as an example thereof, deceleration stop assistance is performed when a vehicle stops at a red signal at an intersection. When the deceleration stop assistance is performed, if there is a gradient in an assistance object interval in front of the intersection, the gravitational acceleration acts on the vehicle according to the gradient, and thus appropriate driving assistance is not possible without considering the gradient. Therefore, the drive assist apparatus disclosed in Patent Literature 1 performs an alert and a brake assist control as driving assistance according to signal cycle information received from a road-side apparatus (an infrastructure), and changes a start-up condition of driving assistance, based on the gradient information received from the road-side apparatus.